The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Tas industry exaggerates RET: think tank

The impact of the renewable energy target on parts of Tasmanian industry has been grossly exaggerated, a left-wing think tank believes.

Four large energy-intensive Tasmanian companies claim the RET costs them $20 million a year, ripping $200 million from the state over 10 years.

The claims have got Tasmanian senator Jacqui Lambie fighting for the target to be scaled back and talking to other crossbenchers about a plan to include existing hydropower and solar schemes in the RET.

The proposal would remove the need for significant investment in renewable energy to meet the target.

But The Australian Institute says claims by the four companies are "gross exaggerations" and the real figure is closer to $8.5 million a year.

The think tank says the RET brings in $125 million to the state, without taking into account jobs and lower electricity prices.

"Claims made against the RET by industry are not free of self-interest," institute senior economist Matt Grudnoff said.